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Summary of Significant Accounting Policies - Schedule of Estimated Useful Life of Property and Equipment (Detail) | 12 Months Ended
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Dec. 31, 2017
Leasehold improvements [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful lives | Shorter of estimated useful life or term of lease
Furniture and equipment [Member] | Minimum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful lives | 3 years
Furniture and equipment [Member] | Maximum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful lives | 10 years
Internal-use software [Member] | Minimum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful lives | 3 years
Internal-use software [Member] | Maximum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful lives | 7 years

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- Definition Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 35 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=68071081&loc=d3e1205-110223 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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- Details
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- Details
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